Ukrainian artillery is at a position outside of the village of Luhanske, some 20 kilometers (14 miles) north of Debaltseve, Ukraine, Tuesday, Feb. 17, 2015. Ukrainian government troops and Russia-backed rebels failed Tuesday to start pulling back heavy weaponry from the front line in eastern Ukraine as a deadline passed to do so. Under a cease-fire agreement negotiated by the leaders of Ukraine, Russia, Germany and France last week, the warring sides were to begin withdrawing heavy weapons from the front line on Tuesday. (AP Photo/Petr David Josek)
(The Associated Press)

Russian Foreign Minister Sergey Lavrov speaks during a meeting with his counterpart from Georgia's breakaway province of South Ossetia David Sanakoyev in Moscow, Russia, Wednesday, Feb. 18, 2015. On Wednesday Lavrov indicated that any solution in Ukraine must protect the rights of all Ukrainian citizens. (AP Photo/Pavel Golovkin)
(The Associated Press)

Ukrainian President Petro Poroshenko speaks to press at Borispol airport outside Kiev, Ukraine on Wednesday, Feb. 18, 2015. The army has withdrawn 80 percent of its troops from the town Debaltseve and two more columns have yet to leave, Ukrainian President Petro Poroshenko said Wednesday. He denied claims by the rebels that the Ukrainians were surrounded and said the troops were leaving Debaltseve with their weapons and ammunition. (AP Photo/Mikhail Palinchak, Presidential Press Service)
(The Associated Press)

VUHLEHIRSK, Ukraine – Ukrainian officials say Russia-back rebels are continuing their onslaught on the railroad junction of Debaltseve, the epicenter of fighting between the separatist and government troops in eastern Ukraine.

Fierce fighting around the town linking two major separatist cities rages on despite a cease-fire which went into effect on Sunday.

Ukrainian military Anatoliy Stelmakh said in a televised briefing on Wednesday that the rebels launched five artillery strikes on Debaltseve overnight.

Hundreds if not thousands of Ukrainian troops are believe to be trapped in Debaltseve, surrounded by advancing rebel troops.

Associated Press reporters were turned back a checkpoint outside Vuhlehirsk, about 10 kilometers (six miles) west of Debaltseve early on Wednesday and were unable to verify the situation there. Regular artillery fire was heard in the vicinity.